Gas capsule

ABSTRACT

A capsule for storing a propellant fluid, for example, helium under pressure comprises a hollow body which includes a frangible area. An anchor member attaches an arm to the frangible area such that when a force is applied to the arm, said force together with the helium under pressure will cause the frangible area to rupture outwardly of the hollow body thereby to release the helium.

The present invention relates to capsules for containing a volume offluid at high pressure, that is, between 60 and 80 bar.

BACKGROUND OF THE INVENTION

The use of sealed capsules is well known in circumstances where theforce of the fluid under pressure is employed to dispense a substancesuch as discharging draught beer from a beer dispenser or expelling sodawater from a soda siphon. They can also be used for liquid containersfor soft drinks or beer under pressure.

It is also known to employ sealed capsules containing helium at highpressures in the order of 30-40 bar in medical devices using the energyof the pressurised helium to drive a therapeutic agent through the skinof a patient.

In PCT published application WO94/24263 there is described a needlelesssyringe, which includes a metal capsule containing helium gas at highpressure which is used to force particles of a therapeutic agent throughthe skin of a patient in a substantially painless manner. The capsule isdetachable from the remainder of the syringe and once used, either a newcharge of gas can be placed in the capsule or more favourably thecapsule can be discarded and a new capsule charged with gas can beattached to the remainder of the syringe.

In the circumstance where the gas capsule is a throw away item, it isimportant that it can be manufactured simply and cheaply. In medicalapplications helium gas is a favoured fluid since it is very light whichmakes it suitable for use as a propellant for therapeutic agents in thatwhen it impinges against the skin of a patient it will bounce off intothe atmosphere and not pass through the skin of the patient. However,helium because it is light, is difficult to contain since it will leakthrough the most minuscule fault in a container.

When the fluid pressure in the container is high the force required tobreak open the seal is often too high for normal "finger pressure" whichis a particular requirement for medical applications.

In accordance with the present invention, there is provided a capsulefor fluid under high pressure which can be manufactured simply andcheaply and can be opened simply by pressing a lever on the outside ofthe capsule. The capsules of the invention are further advantageous inthat they can contain a fluid under pressure for example, helium gas,yet are substantially leak-proof and can be easily opened by pressurefrom a normal adult finger (2 kg).

SUMMARY OF THE INVENTION

According to the present invention, a capsule for storing a fluid at apressure of at least 60 bar comprises a hollow body, the hollow bodyincluding a frangible area, means for fixedly attaching an arm to thefrangible area such that the arm is spaced from and extends outwardly ofthe hollow body, the arrangement being such that a predetermined forceapplied to the arm in the direction of the hollow body will, togetherwith the fluid pressure, cause the frangible area to rupture outwardlywith the subsequent release of the fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial side view partly in cross-section of a first capsulefor storing a fluid under pressure;

FIG. 2 is a view similar to FIG. 1 but illustrating a differentarrangement of the arm for opening the capsule; and

FIG. 3 is a view similar to FIG. 1 but illustrating a differentembodiment of a sealed capsule for storing a fluid under pressure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIGS. 1 and 2, a sealed metal capsule 1 comprises asubstantially cylindrical hollow body 2 for containing a fluid e.g.helium gas, under high pressures in the order of 60-80 bar. The hollowbody 2 is provided at its upper (as shown ) end with a frangible area 4.The frangible area 4 is formed by reducing the wall thickness at theupper end of the hollow body 2 over a portion of said end. An arm 6 isfixedly mounted to the outer surface of the frangible area 4 by means ofan anchor member 8.

The frangible area 4 is defined at least in part by a weakened portion 3which acts as a `hinge` and a further portion 5 even more weakened wherefracture commences as will be explained.

As shown in both FIGS., the arm is preferably mounted in cantileverfashion spaced from and extending outwardly from the upper end of thebody 2 and the load is applied at or adjacent the free end of the arm ina direction towards the hollow body

In use, when the energy of the fluid contained within the hollow body 2is to be employed to dispense a substance or force particles of atherapeutic agent through the skin of a patient, then a force `P` isapplied at or adjacent the free end of the arm 6 which will cause thefrangible area 4 to fracture initially at the portion 5, the portion 3acting as a hinge. The fluid under pressure is thereby released from thehollow body 2 of the capsule 1.

It should be noted that in the above described embodiments, the energyof the fluid e.g. helium gas under pressure assists in the rupturingprocess in that it provides a force tending to lift the frangible area 4from the remainder of the upper end of the hollow body 2.

It will be appreciated that the capsules described with reference toFIGS. 1 and 2 are relatively inexpensive to manufacture and furthermoreare relatively leak-proof.

FIG. 3 illustrates an alternative embodiment wherein the arm can bemounted for pivoted movement on the frangible area and may include afoot part located inside the hollow body having an edge for engaging aportion of the frangible area. Referring to FIG. 3, where like referencenumerals denote like parts, the cylindrical hollow body 2 is provided atits upper (as shown) end with a frangible area 4. The frangible area 4is defined at least in part by a first weakened portion 3 and a secondportion 5 even more weakened. An arm 6 is mounted for pivotal movementabout a pivot point 8 on the frangible area 4 and includes a lower (asshown) foot part 9 extending into the interior of the hollow body 2. Thefoot part 9 includes an edge 10 substantially aligned with the secondportion 5 of the frangible area 4.

In use, when the energy of the fluid contained within the hollow body 2is to be utilised to dispense a substance e.g. soda water or forceparticles of a therapeutic agent through the skin of a patient, then aforce `P` is applied at or adjacent the free end of the arm 6 which willpivot about the pivot point 8 thereby causing the edge 10 of the footpart 9 to engage and rupture the frangible area 4 initially at thesecond weakened portion 5. The pivotal action of the arm 6 together withthe pressure of the fluid e.g. helium at between 60 and 80 bar willcontinue the rupturing process with the frangible area 4 being pivotedaround the first weakened portion 3 which acts as a hinge. The fluidwill thus be released under pressure from the hollow body 2 of thecapsule 1.

Although reference has been made to the use of the capsules with aneedle-less syringe for medical purposes, there are a number of otherapplications where the force of the contained fluid can be utilised. Forexample, in the inflation of balloons bearing fluorescent markings foridentification by radar and for the inflation of life jackets anddinghies.

The energy of the pressurized fluid could also be utilized in a weaponto act as a propellant for a bullet or other projectile.

We claim:
 1. A capsule containing helium comprising a hollow body, afrangible area formed on a surface of the hollow body, a cantilever armand means for fixedly attaching the cantilever arm to the frangible areasuch that the arm is spaced from and extends outwardly of the hollowbody such that a force, when applied at or adjacent the free end of thecantilever arm in the direction towards the hollow body, will, togetherwith the pressure of the helium in the hollow body, cause the frangiblearea to rupture outwardly with the subsequent release of the helium. 2.A capsule in accordance with claim 1 wherein the helium gas inside thehollow body is at a pressure of at least 60 bar.
 3. A capsule inaccordance with claim 1, wherein the frangible area has an outer surfaceand the means for fixedly attaching the cantilever arm to the frangiblearea is an anchor member located on the outer surface of the frangiblearea.
 4. A capsule in accordance with claim 1, wherein the frangiblearea is defined at least in part by a first weakened portion and asecond portion even more weakened than the first weakened portion.
 5. Acapsule in accordance with claim 4, wherein the arm is mounted forpivotal movement on the frangible area and includes a foot part locatedinside the hollow body having an edge for engaging the second portion ofthe frangible area.